Such systems are used, for example, as a component of paint systems. In such paint systems, the substrate surface is typically cleaned in a first step. This can be done, for example, with air pressure and/or with means for ionizing the surface or by blasting the surface with a liquid medium such as water or an aqueous, alcohol-based, or solvent-containing solution or with a solid such as blasting material or CO2, or by immersing the substrate in an aqueous, alcohol-based, or solvent-containing solution, possibly with the action of waves such as ultrasound waves or microwaves.
In the case of cleaning with liquid media, IR heat waves can even be used for the subsequent drying.
In a second step, the actual paint layer can then be applied according to the invention by spraying on a paint dispersion. This is followed by a step in which the already painted substrate is baked. This can be carried out by means of heating in the ambient air and/or by applying infrared radiation (IR) for example at 50-80° C. This causes the solvent that is usually present in the paint dispersion to evaporate. In the UV-hardened paints that are widely used today, i.e. paints that are cured by means of UV light, this hardening takes place in a step following the volatilization of the solvent. Depending on the application. IR- and/or UV lamps are used in these process steps. In the present description, the process of drying by means of IR radiation and/or the process of curing by means of UV radiation are uniformly referred to as radiation treatment.
In order to prevent solvents from volatilizing freely into the environment and into the work environment, according to the prior art, such processes are carried out in treatment chambers.
This is intended to ensure that a continuous gas exchange takes place in order, for example, to minimize the solvent concentration in the vicinity of the substrate and thus to also accelerate the drying and/or curing process. According to the prior art, as schematically depicted in FIG. 1, the radiation treatment is carried out in a closed chamber 1. The radiation source 9, 9′, 9″ is provided in the upper pan of the chamber 1 and the substrate holders 11, 11′ that are to be equipped with substrates are placed in the lower part. FIG. 1 shows substrate holders in the form of two spindles, which can be equipped with components that are to be irradiated. It would also be possible to place the radiation sources 9, 9′, 9″ below the substrate holders 11, 11′, but this is generally avoided in order not to run the risk of the radiation sources 9, 9′, 9″ being soiled by paint residues that drip from the substrates.
According to the prior art, the chamber ceiling is provided with an inflow region 7 through which gas, e.g. air, that is fed from an inlet 3 flows into the chamber. According to the prior art, the gas flows past the radiation sources 9, 9′, 9″ and then past the substrates 11, 11′ and into the lower region of the chamber where it is aspirated from the chamber 1 via the outlet 5. Because of this placement according to the prior art, flow and gravity work together so that impurities such as dust and solvent are effectively aspirated away. The gas flow and its direction are schematically depicted by means of arrows in FIG. 1.
The arrangement according to the prior art, however, is disadvantageous in that the gas flow that flows past the substrates must first pass the radiation sources. These are generally hot during operation, which leads to an uncontrolled heating of the gas flow. This means that the substrate holders 11, 11′ are acted on by a gas flow that has an indefinite temperature and temperature gradients can even occur across the width of the substrate holders. The process of the drying, and/or curing, however, is strongly influenced by the prevailing temperature. Indefinite temperature conditions therefore very quickly result in an uncontrolled process. Irregularities occur particularly if there are temperature gradients. The problem becomes even more pronounced due to the fact that the radiation sources themselves are generally not temperature-stabilized. In the starting phase, the radiation sources are rather cool, but the heat up considerably after long operation. This problem could in fact be reduced by means of explicit cooling steps carried out at the radiation sources. Such steps, however, involve significant technical complexity and are therefore costly.
According to the foregoing, it would be desirable to have radiation treatment equipment available that could be used to reduce and preferably completely overcome the above-mentioned problems of the prior art.
The object of the invention, therefore, is to create such a system.